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  • Nyquist won't play audio

    - by erjiang
    I downloaded Nyquist, and am having trouble playing sounds from it. If I run it normally, I get: Nyquist -- A Language for Sound Synthesis and Composition Copyright (c) 1991,1992,1995 by Roger B. Dannenberg Version 2.29 > (play (osc 60)) Saving sound file to ./eric-temp.wav error: snd_save -- could not open audio output > If I wrap it by running padsp ny, the sound plays fine for about half a second, and then I get garbage fed to my speakers. Any solutions?

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  • Free eBook with SQL Server performance tips and nuggets

    - by Claire Brooking
    I’ve often found that the kind of tips that turn out to be helpful are the ones that encourage me to make a small step outside of a routine. No dramatic changes – just a quick suggestion that changes an approach. As a languages student at university, one of the best I spotted came from outside the lecture halls and ended up saving me time (and lots of huffing and puffing) – the use of a rainbow of sticky notes for well-used pages and letter categories in my dictionary. Simple, but armed with a heavy dictionary that could double up as a step stool, those markers were surprisingly handy. When the Simple-Talk editors told me about a book they were planning that would give a series of tips for developers on how to improve database performance, we all agreed it needed to contain a good range of pointers for big-hitter performance topics. But we wanted to include some of the smaller, time-saving nuggets too. We hope we’ve struck a good balance. The 45 Database Performance Tips eBook covers different tips to help you avoid code that saps performance, whether that’s the ‘gotchas’ to be aware of when using Object to Relational Mapping (ORM) tools, or what to be aware of for indexes, database design, and T-SQL. The eBook is also available to download with SQL Prompt from Red Gate. We often hear that it’s the productivity-boosting side of SQL Prompt that makes it useful for everyday coding. So when a member of the SQL Prompt team mentioned an idea to make the most of tab history, a new feature in SQL Prompt 6 for SQL Server Management Studio, we were intrigued. Now SQL Prompt can save tabs we have been working on in SSMS as a way to maintain an active template for queries we often recycle. When we need to reuse the same code again, we search for our saved tab (and we can also customize its name to speed up the search) to get started. We hope you find the eBook helpful, and as always on Simple-Talk, we’d love to hear from you too. If you have a performance tip for SQL Server you’d like to share, email Melanie on the Simple-Talk team ([email protected]) and we’ll publish a collection in a follow-up post.

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  • T-SQL Tuesday 24: Ode to Composable Code

    - by merrillaldrich
    I love the T-SQL Tuesday tradition, started by Adam Machanic and hosted this month by Brad Shulz . I am a little pressed for time this month, so today’s post is a short ode to how I love saving time with Composable Code in SQL. Composability is one of the very best features of SQL, but sometimes gets picked on due to both real and imaginary performance worries. I like to pick composable solutions when I can, while keeping the perf issues in mind, because they are just so handy and eliminate so much...(read more)

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  • Cannot save tar.gz file to usr/local

    - by ATMathew
    I'm using the following instruction to install and configure Hadoop on Ubuntu 10.10. http://www.michael-noll.com/tutorials/running-hadoop-on-ubuntu-linux-single-node-cluster/#installation I tried to save the compressed tar.gz file to /usr/local/ but it just won't save. I've tried saving the tar.gz in my home folder and desktop and copying the files to the desired folder, but I get an error that tells me I don't have permission. How do I save and extract a tar.gz folder to /usr/local/hadoop?

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  • Apache could not reliably determine server

    - by frqcuse
    Apache cannot fully determine domain name when I tried restarting after install. I get this error; sudo /etc/init.d/apache2 restart *Restarting web server config apache2 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName. Why I'm I seeing 127.0.1.1 I have tried saving ServerName localhost into my /etc/init.d/apache2 but it keeps redirecting me to google search page everytime I type phpmyadmin. Will appreciate an expert help?

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  • External USB 3 drive not recognized

    - by ilan123
    Ubuntu 12.10 64 bit seems not to recognize my external hard disk. It is a Vantec NST-310S3 external disk enclosure with a WD 3TB drive. The disk has two NTFS partitions. My PC is a dual boot system. Under Windows 7 the hard disk works fine but I can't make it work with Ubuntu. When the drive is connected to the PC then the command sudo fdisk -l seems to hang forever. Below are the output of lsusb and cat /proc/partitions without the external drive and then with it connected. I added also the last lines of the dmesg command at the end. First without the drive: ilan@linux:~$ lsusb Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 003: ID 13ba:0017 Unknown PS/2 Keyboard+Mouse Adapter Bus 001 Device 004: ID 046d:c50e Logitech, Inc. Cordless Mouse Receiver Bus 001 Device 005: ID 0ac8:3420 Z-Star Microelectronics Corp. Venus USB2.0 Camera ilan@linux:~$ cat /proc/partitions major minor #blocks name 8 0 1953514584 sda 8 1 102400 sda1 8 2 629043200 sda2 8 3 367001600 sda3 8 4 1 sda4 8 5 471859200 sda5 8 6 157286400 sda6 8 7 324115456 sda7 8 8 4101120 sda8 11 0 1048575 sr0 Second with the USB 3 drive: ilan@linux:~$ lsusb Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 004 Device 002: ID 174c:55aa ASMedia Technology Inc. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 003: ID 13ba:0017 Unknown PS/2 Keyboard+Mouse Adapter Bus 001 Device 004: ID 046d:c50e Logitech, Inc. Cordless Mouse Receiver Bus 001 Device 005: ID 0ac8:3420 Z-Star Microelectronics Corp. Venus USB2.0 Camera ilan@linux:~$ cat /proc/partitions major minor #blocks name 8 0 1953514584 sda 8 1 102400 sda1 8 2 629043200 sda2 8 3 367001600 sda3 8 4 1 sda4 8 5 471859200 sda5 8 6 157286400 sda6 8 7 324115456 sda7 8 8 4101120 sda8 11 0 1048575 sr0 8 16 2930266584 sdb ilan@linux:~$ lsusb -v -s 004:002 Bus 004 Device 002: ID 174c:55aa ASMedia Technology Inc. Couldn't open device, some information will be missing Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 3.00 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 9 idVendor 0x174c ASMedia Technology Inc. idProduct 0x55aa bcdDevice 1.00 iManufacturer 2 iProduct 3 iSerial 1 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 44 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0xc0 Self Powered MaxPower 0mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 2 bInterfaceClass 8 Mass Storage bInterfaceSubClass 6 SCSI bInterfaceProtocol 80 Bulk-Only iInterface 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x81 EP 1 IN bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0400 1x 1024 bytes bInterval 0 bMaxBurst 15 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x02 EP 2 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0400 1x 1024 bytes bInterval 0 bMaxBurst 15 ilan@linux:~$ sudo fdisk -l [sudo] password for ilan: Disk /dev/sda: 2000.4 GB, 2000398934016 bytes 255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xf1b4f1ee Device Boot Start End Blocks Id System /dev/sda1 * 2048 206847 102400 7 HPFS/NTFS/exFAT /dev/sda2 206848 1258293247 629043200 7 HPFS/NTFS/exFAT /dev/sda3 1258293248 1992296447 367001600 7 HPFS/NTFS/exFAT /dev/sda4 1992298494 3907028991 957365249 f W95 Ext'd (LBA) /dev/sda5 1992298496 2936016895 471859200 7 HPFS/NTFS/exFAT /dev/sda6 2936018944 3250591743 157286400 7 HPFS/NTFS/exFAT /dev/sda7 3250593792 3898824703 324115456 83 Linux /dev/sda8 3898826752 3907028991 4101120 82 Linux swap / Solaris dmesg output after connecting the external drive: [ 23.740567] e1000e: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: Rx/Tx [ 23.740786] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready [ 49.144673] usb 4-1: >new SuperSpeed USB device number 2 using xhci_hcd [ 49.163039] usb 4-1: >Parent hub missing LPM exit latency info. Power management will be impacted. [ 49.166789] usb 4-1: >New USB device found, idVendor=174c, idProduct=55aa [ 49.166793] usb 4-1: >New USB device strings: Mfr=2, Product=3, SerialNumber=1 [ 49.166796] usb 4-1: >Product: AS2105 [ 49.166799] usb 4-1: >Manufacturer: ASMedia [ 49.166801] usb 4-1: >SerialNumber: 0123456789ABCDEF [ 49.206372] usbcore: registered new interface driver uas [ 49.228891] Initializing USB Mass Storage driver... [ 49.229042] scsi6 : usb-storage 4-1:1.0 [ 49.229115] usbcore: registered new interface driver usb-storage [ 49.229116] USB Mass Storage support registered. [ 64.045528] scsi 6:0:0:0: >Direct-Access WDC WD30 EZRX-00MMMB0 80.0 PQ: 0 ANSI: 0 [ 64.046224] sd 6:0:0:0: >Attached scsi generic sg2 type 0 [ 64.046881] sd 6:0:0:0: >[sdb] Very big device. Trying to use READ CAPACITY(16). [ 64.047610] sd 6:0:0:0: >[sdb] 5860533168 512-byte logical blocks: (3.00 TB/2.72 TiB) [ 64.048368] sd 6:0:0:0: >[sdb] Write Protect is off [ 64.048373] sd 6:0:0:0: >[sdb] Mode Sense: 23 00 00 00 [ 64.048984] sd 6:0:0:0: >[sdb] No Caching mode page present [ 64.048987] sd 6:0:0:0: >[sdb] Assuming drive cache: write through [ 64.049297] sd 6:0:0:0: >[sdb] Very big device. Trying to use READ CAPACITY(16). [ 64.050942] sd 6:0:0:0: >[sdb] No Caching mode page present [ 64.050944] sd 6:0:0:0: >[sdb] Assuming drive cache: write through [ 94.245006] usb 4-1: >reset SuperSpeed USB device number 2 using xhci_hcd [ 94.262553] usb 4-1: >Parent hub missing LPM exit latency info. Power management will be impacted. [ 94.263805] xhci_hcd 0000:03:00.0: >xHCI xhci_drop_endpoint called with disabled ep ffff8800d37d1c00 [ 94.263808] xhci_hcd 0000:03:00.0: >xHCI xhci_drop_endpoint called with disabled ep ffff8800d37d1c40 [ 125.262722] usb 4-1: >reset SuperSpeed USB device number 2 using xhci_hcd [ 125.280304] usb 4-1: >Parent hub missing LPM exit latency info. Power management will be impacted. [ 125.281511] xhci_hcd 0000:03:00.0: >xHCI xhci_drop_endpoint called with disabled ep ffff8800d37d1c00 [ 125.281516] xhci_hcd 0000:03:00.0: >xHCI xhci_drop_endpoint called with disabled ep ffff8800d37d1c40

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  • How can I replicate Google Page Speed's lossless image compression as part of my workflow?

    - by Keefer
    I love that Google's Page Speed is able to losslessly compress a lot of my images, but I'd love to make it part of my workflow, prior to uploading a site and making it live. Is there anything I can run locally to give me the same lossless compression? I currently export images from Export For Web from Photoshop, and use a little application called PNGCrusher to reduce file size of PNGs. I'd love to find a faster way though than saving out and replacing the individual images from Page Speed's results.

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  • Maya .IFF plugins for Gimp

    - by Kara Marfia
    Maya's preferred format for saving off a UV Snapshot is its own .IFF format, so I was hoping to find a plugin allowing Gimp 2 (Windows) to read it. I've found plenty of plugins for different linux distros, but none are win-friendly (that I can discern - admittedly I'm no whiz with Gimp). Does anyone know of one? Alternately, .tiff seems to work just fine, so if there's no good reason to bother fiddling with IFFs, I'd appreciate the input there, too. (sorry if this isn't on-topic)

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  • AppHarbor - Azure Done Right AKA Heroku for .NET

    - by Robz / Fervent Coder
    Easy and Instant deployments and instant scale for .NET? Awhile back a few of us were looking at Ruby Gems as the answer to package management for .NET. The gems platform supported the concept of DLLs as packages although some changes would have needed to happen to have long term use for the entire community. From that we formed a partnership with some folks at Microsoft to make v2 into something that would meet wider adoption across the community, which people now call NuGet. So now we have the concept of package management. What comes next? Heroku Instant deployments and instant scaling. Stupid simple API. This is Heroku. It doesn’t sound like much, but when you think of how fast you can go from an idea to having someone else tinker with it, you can start to see its power. In literally seconds you can be looking at your rails application deployed and online. Then when you are ready to scale, you can do that. This is power. Some may call this “cloud-computing” or PaaS (Platform as a Service). I first ran into Heroku back in July when I met Nick of RubyGems.org. At the time there was no alternative in the .NET-o-sphere. I don’t count Windows Azure, mostly because it is not simple and I don’t believe there is a free version. Heroku itself would not lend itself well to .NET due to the nature of platforms and each language’s specific needs (solution stack).  So I tucked the idea in the back of my head and moved on. AppHarbor Enters The Scene I’m not sure when I first heard about AppHarbor as a possible .NET version of Heroku. It may have been in November, but I didn’t actually try it until January. I was instantly hooked. AppHarbor is awesome! It still has a ways to go to be considered Heroku for .NET, but it already has a growing community. I created a video series (at the bottom of this post) that really highlights how fast you can get a product onto the web and really shows the power and simplicity of AppHarbor. Deploying is as simple as a git/hg push to appharbor. From there they build your code, run any unit tests you have and deploy it if everything succeeds. The screen on the right shows a simple and elegant UI to getting things done. The folks at AppHarbor graciously gave me a limited number of invites to hand out. If you are itching to try AppHarbor then navigate to: https://appharbor.com/account/new?inviteCode=ferventcoder  After playing with it, send feedback if you want more features. Go vote up two features I want that will make it more like Heroku. Disclaimer: I am in no way affiliated with AppHarbor and have not received any funds or favors from anyone at AppHarbor. I just think it is awesome and I want others to know about it. From Zero To Deployed in 15 Minutes (Or Less) Now I have a challenge for you. I created a video series showing how fast I could go from nothing to a deployed application. It could have been from Zero to Deployed in Less than 5 minutes, but I wanted to show you the tools a little more and give you an opportunity to beat my time. And that’s the challenge. Beat my time and show it in a video response. The video series is below (at least one of the videos has to be watched on YouTube). The person with the best time by March 15th @ 11:59PM CST will receive a prize. Ground rules: .NET Application with a valid database connection Start from Zero Deployed with AppHarbor or an alternative A timer displayed in the video that runs during the entire process Video response published on YouTube or acceptable alternative Video(s) must be published by March 15th at 11:59PM CST. Either post the link here as a comment or on YouTube as a response (also by 11:59PM CST March 15th) From Zero To Deployed In 15 Minutes (Or Less) Part 1 From Zero To Deployed In 15 Minutes (Or Less) Part 2 From Zero To Deployed In 15 Minutes (Or Less) Part 3

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  • Session Report - Java on the Raspberry Pi

    - by Janice J. Heiss
    On mid-day Wednesday, the always colorful Oracle Evangelist Simon Ritter demonstrated Java on the Raspberry Pi at his session, “Do You Like Coffee with Your Dessert?”. The Raspberry Pi consists of a credit card-sized single-board computer developed in the UK with the intention of stimulating the teaching of basic computer science in schools. “I don't think there is a single feature that makes the Raspberry Pi significant,” observed Ritter, “but a combination of things really makes it stand out. First, it's $35 for what is effectively a completely usable computer. You do have to add a power supply, SD card for storage and maybe a screen, keyboard and mouse, but this is still way cheaper than a typical PC. The choice of an ARM (Advanced RISC Machine and Acorn RISC Machine) processor is noteworthy, because it avoids problems like cooling (no heat sink or fan) and can use a USB power brick. When you add in the enormous community support, it offers a great platform for teaching everyone about computing.”Some 200 enthusiastic attendees were present at the session which had the feel of Simon Ritter sharing a fun toy with friends. The main point of the session was to show what Oracle was doing to support Java on the Raspberry Pi in a way that is entertaining and fun. Ritter pointed out that, in addition to being great for teaching, it’s an excellent introduction to the ARM architecture, and runs well with Java and will get better once it has official hard float support. The possibilities are vast.Ritter explained that the Raspberry Pi Project started in 2006 with the goal of devising a computer to inspire children; it drew inspiration from the BBC Micro literacy project of 1981 that produced a series of microcomputers created by the Acorn Computer company. It was officially launched on February 29, 2012, with a first production of 10,000 boards. There were 100,000 pre-orders in one day; currently about 4,000 boards are produced a day. Ritter described the specification as follows:* CPU: ARM 11 core running at 700MHz Broadcom SoC package Can now be overclocked to 1GHz (without breaking the warranty!) * Memory: 256Mb* I/O: HDMI and composite video 2 x USB ports (Model B only) Ethernet (Model B only) Header pins for GPIO, UART, SPI and I2C He took attendees through a brief history of ARM Architecture:* Acorn BBC Micro (6502 based) Not powerful enough for Acorn’s plans for a business computer * Berkeley RISC Project UNIX kernel only used 30% of instruction set of Motorola 68000 More registers, less instructions (Register windows) One chip architecture to come from this was… SPARC * Acorn RISC Machine (ARM) 32-bit data, 26-bit address space, 27 registers First machine was Acorn Archimedes * Spin off from Acorn, Advanced RISC MachinesNext he presented its features:* 32-bit RISC Architecture–  ARM accounts for 75% of embedded 32-bit CPUs today– 6.1 Billion chips sold last year (zero manufactured by ARM)* Abstract architecture and microprocessor core designs– Raspberry Pi is ARM11 using ARMv6 instruction set* Low power consumption– Good for mobile devices– Raspberry Pi can be powered from 700mA 5V only PSU– Raspberry Pi does not require heatsink or fanHe described the current ARM Technology:* ARMv6– ARM 11, ARM Cortex-M* ARMv7– ARM Cortex-A, ARM Cortex-M, ARM Cortex-R* ARMv8 (Announced)– Will support 64-bit data and addressingHe next gave the Java Specifics for ARM: Floating point operations* Despite being an ARMv6 processor it does include an FPU– FPU only became standard as of ARMv7* FPU (Hard Float, or HF) is much faster than a software library* Linux distros and Oracle JVM for ARM assume no HF on ARMv6– Need special build of both– Raspbian distro build now available– Oracle JVM is in the works, release date TBDNot So RISCPerformance Improvements* DSP Enhancements* Jazelle* Thumb / Thumb2 / ThumbEE* Floating Point (VFP)* NEON* Security Enhancements (TrustZone)He spent a few minutes going over the challenges of using Java on the Raspberry Pi and covered:* Sound* Vision * Serial (TTL UART)* USB* GPIOTo implement sound with Java he pointed out:* Sound drivers are now included in new distros* Java Sound API– Remember to add audio to user’s groups– Some bits work, others not so much* Playing (the right format) WAV file works* Using MIDI hangs trying to open a synthesizer* FreeTTS text-to-speech– Should work once sound works properlyHe turned to JavaFX on the Raspberry Pi:* Currently internal builds only– Will be released as technology preview soon* Work involves optimal implementation of Prism graphics engine– X11?* Once the JavaFX implementation is completed there will be little of concern to developers-- It’s just Java (WORA). He explained the basis of the Serial Port:* UART provides TTL level signals (3.3V)* RS-232 uses 12V signals* Use MAX3232 chip to convert* Use this for access to serial consoleHe summarized his key points. The Raspberry Pi is a very cool (and cheap) computer that is great for teaching, a great introduction to ARM that works very well with Java and will work better in the future. The opportunities are limitless. For further info, check out, Raspberry Pi User Guide by Eben Upton and Gareth Halfacree. From there, Ritter tried out several fun demos, some of which worked better than others, but all of which were greeted with considerable enthusiasm and support and good humor (even when he ran into some glitches).  All in all, this was a fun and lively session.

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  • Rotating Oracle Database's Alert Log with ADRCI

    Many Oracle database administrators would not only like to report on (ORA-) errors but also manage the alert log itself--saving and/or trimming the alert log, aka alert log rotation. Oracle's new ADR with command interface can easily be used to help rotate Oracle's alert log.

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  • Ubuntu won't save my settings for thinkpad trackpoint

    - by serve.chilled
    I'm using Ubuntu 12.04 on a Thinkpad X200. To configure the trackpoint, I use "configure TrackPoint". Unfortunately I can't make Ubuntu saving my settings (concerning the sensitivity etc.). Whenever I reboot the computer, it's set to generic settings again. I already tried htorque's answer to a similar question and created a new udev-rule for the trackpoint-settings but it didn't helped. So, how can I make theses settings permanent?

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  • Storing application preferences and data

    - by Rudi Strydom
    I am looking at creating some Ubuntu applications, but finding good resoures are hard. I am using the quickly toolkit, but would really like some more insight. How does one normally store application preferences and settings in Linux / Ubuntu. Is it as simple as creating a XML file and saving the information and then reading from said file on application bootstrap? If someone can point me in a direction it would be greatly appreciated.

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  • Class instance clustering in object reference graph for multi-entries serialization

    - by Juh_
    My question is on the best way to cluster a graph of class instances (i.e. objects, the graph nodes) linked by object references (the -directed- edges of the graph) around specifically marked objects. To explain better my question, let me explain my motivation: I currently use a moderately complex system to serialize the data used in my projects: "marked" objects have a specific attributes which stores a "saving entry": the path to an associated file on disc (but it could be done for any storage type providing the suitable interface) Those object can then be serialized automatically (eg: obj.save()) The serialization of a marked object 'a' contains implicitly all objects 'b' for which 'a' has a reference to, directly s.t: a.b = b, or indirectly s.t.: a.c.b = b for some object 'c' This is very simple and basically define specific storage entries to specific objects. I have then "container" type objects that: can be serialized similarly (in fact their are or can-be "marked") they don't serialize in their storage entries the "marked" objects (with direct reference): if a and a.b are both marked, a.save() calls b.save() and stores a.b = storage_entry(b) So, if I serialize 'a', it will serialize automatically all objects that can be reached from 'a' through the object reference graph, possibly in multiples entries. That is what I want, and is usually provides the functionalities I need. However, it is very ad-hoc and there are some structural limitations to this approach: the multi-entry saving can only works through direct connections in "container" objects, and there are situations with undefined behavior such as if two "marked" objects 'a'and 'b' both have a reference to an unmarked object 'c'. In this case my system will stores 'c' in both 'a' and 'b' making an implicit copy which not only double the storage size, but also change the object reference graph after re-loading. I am thinking of generalizing the process. Apart for the practical questions on implementation (I am coding in python, and use Pickle to serialize my objects), there is a general question on the way to attach (cluster) unmarked objects to marked ones. So, my questions are: What are the important issues that should be considered? Basically why not just use any graph parsing algorithm with the "attach to last marked node" behavior. Is there any work done on this problem, practical or theoretical, that I should be aware of? Note: I added the tag graph-database because I think the answer might come from that fields, even if the question is not.

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  • boot issues - long delay, then "gave up waiting for root device"

    - by chazomaticus
    I've had this issue on and off for about two years now. I noticed it on a new (custom built) machine running 10.04 when that first came out, but then it went away until a few months ago. I've gone through a number of hard drive changes but I can't say specifically what if anything I changed hardware-wise to make it stop or start happening. I had assumed upgrading to a modern Ubuntu version would fix the issue, so I installed 12.04 beta on a spare partition last night, but it's still happening. Here's the issue. After grub loads and I select a kernel to boot, the screen goes blank save for a blinking cursor. It sits in this state for many long minutes before it finally gives up and gives me an initramfs shell with the message gave up waiting for root device (and lists the /dev/disk/by-uuid/... path it was waiting for) but no other specific diagnostic information. Now, here's the tricky part. For one, the problem is intermittent - sometimes it progresses from the blinking cursor to the Ubuntu splash boot screen in a few seconds, and once it gets that far it always continues booting fine. The really bizarre thing is that I can "force" it to "find" the root device by repeatedly pressing the space bar and hitting the machine's power button. If I tap those enough, eventually I will notice the hard drive light coming on, at which point it will always continue the boot process after a few seconds. Interestingly, if I wait slightly too long before pressing the power button (30s?), as soon as I press it I get the gave up waiting message and the initramfs shell. I've tried setting up /etc/fstab (and the grub menu.lst or whatever it's called nowadays) to use device names (e.g. /dev/sda1) instead of UUIDs, but I get the same effect just with the device name, not UUID, in the error message. I should also mention that when I boot to Windows 7, there is no issue. It boots slowly all the time just by virtue of being Windows, but it never hangs indefinitely. This would seem to indicate it's a problem in Ubuntu, not the hardware. It's pretty annoying to have to babysit the computer every time it boots. Any ideas? I'm at a loss. Not even sure how to diagnose the issue. Thanks! EDIT: Here's some dmesg output from 10.04. The 15 second gap is where it was doing nothing. I pressed the power button and space bar a few times, and the stuff at 16 seconds happened. Not sure what any of it means. [ 1.320250] scsi18 : ahci [ 1.320294] scsi19 : ahci [ 1.320320] ata19: SATA max UDMA/133 abar m8192@0xfd4fe000 port 0xfd4fe100 ir q 18 [ 1.320323] ata20: SATA max UDMA/133 abar m8192@0xfd4fe000 port 0xfd4fe180 ir q 18 [ 1.403886] usb 2-4: new high speed USB device using ehci_hcd and address 4 [ 1.562558] usb 2-4: configuration #1 chosen from 1 choice [ 16.477824] ata16: SATA link down (SStatus 0 SControl 300) [ 16.477843] ata19: SATA link down (SStatus 0 SControl 300) [ 16.477857] ata3: SATA link down (SStatus 0 SControl 300) [ 16.477895] ata15: SATA link down (SStatus 0 SControl 300) [ 16.477906] ata20: SATA link down (SStatus 0 SControl 300) [ 16.477977] ata17: SATA link down (SStatus 0 SControl 300) [ 16.478003] ata12: SATA link down (SStatus 0 SControl 300) [ 16.478046] ata13: SATA link down (SStatus 0 SControl 300) [ 16.478063] ata14: SATA link down (SStatus 0 SControl 300) [ 16.478108] ata11: SATA link down (SStatus 0 SControl 300) [ 16.478123] ata18: SATA link up 1.5 Gbps (SStatus 113 SControl 300) [ 16.478127] ata6: SATA link down (SStatus 0 SControl 300) [ 16.478157] ata5: SATA link down (SStatus 0 SControl 300) [ 16.478193] ata18.00: ATAPI: MARVELL VIRTUALL, 1.09, max UDMA/66 After that, it took its sweet time, and I had to keep hitting space bar to coax it along. Here's some more dmesg output from a little later in the boot process: [ 17.982291] input: BTC USB Multimedia Keyboard as /devices/pci0000:00/0000:00 :13.0/usb5/5-2/5-2:1.0/input/input4 [ 17.982335] generic-usb 0003:046E:5506.0002: input,hidraw1: USB HID v1.10 Key board [BTC USB Multimedia Keyboard] on usb-0000:00:13.0-2/input0 [ 18.005211] input: BTC USB Multimedia Keyboard as /devices/pci0000:00/0000:00 :13.0/usb5/5-2/5-2:1.1/input/input5 [ 18.005274] generic-usb 0003:046E:5506.0003: input,hiddev96,hidraw2: USB HID v1.10 Device [BTC USB Multimedia Keyboard] on usb-0000:00:13.0-2/input1 [ 22.484906] EXT4-fs (sda6): INFO: recovery required on readonly filesystem [ 22.484910] EXT4-fs (sda6): write access will be enabled during recovery [ 22.548542] EXT4-fs (sda6): recovery complete [ 22.549074] EXT4-fs (sda6): mounted filesystem with ordered data mode [ 32.516772] Adding 20482832k swap on /dev/sda5. Priority:-1 extents:1 across:20482832k [ 32.742540] udev: starting version 151 [ 33.002004] Bluetooth: Atheros AR30xx firmware driver ver 1.0 [ 33.008135] parport_pc 00:09: reported by Plug and Play ACPI [ 33.008186] parport0: PC-style at 0x378, irq 7 [PCSPP,TRISTATE] [ 33.012076] lp: driver loaded but no devices found [ 33.037271] ppdev: user-space parallel port driver [ 33.090256] lp0: using parport0 (interrupt-driven). Any clues in there?

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  • A sample Memento pattern: Is it correct?

    - by TheSilverBullet
    Following this query on memento pattern, I have tried to put my understanding to test. Memento pattern stands for three things: Saving state of the "memento" object for its successful retrieval Saving carefully each valid "state" of the memento Encapsulating the saved states from the change inducer so that each state remains unaltered Have I achieved these three with my design? Problem This is a zero player game where the program is initialized with a particular set up of chess pawns - the knight and queen. Then program then needs to keep adding set of pawns or knights and queens so that each pawn is "safe" for the next one move of every other pawn. The condition is that either both pawns should be placed, or none of them should be placed. The chessboard with the most number of non conflicting knights and queens should be returned. Implementation I have 4 classes for this: protected ChessBoard (the Memento) private int [][] ChessBoard; public void ChessBoard(); protected void SetChessBoard(); protected void GetChessBoard(int); public Pawn This is not related to memento. It holds info about the pawns public enum PawnType: int { Empty = 0, Queen = 1, Knight = 2, } //This returns a value that shown if the pawn can be placed safely public bool IsSafeToAddPawn(PawnType); public CareTaker This corresponds to caretaker of memento This is a double dimentional integer array that keeps a track of all states. The reason for having 2D array is to keep track of how many states are stored and which state is currently active. An example: 0 -2 1 -1 2 0 - This is current state. With second index 0/ 3 1 - This state has been saved, but has been undone private int [][]State; private ChessBoard [] MChessBoard; //This gets the chessboard at the position requested and assigns it to originator public ChessBoard GetChessBoard(int); //This overwrites the chessboard at given position public void SetChessBoard(ChessBoard, int); private int [][]State; public PlayGame (This is the originator) private bool status; private ChessBoard oChessBoard; //This sets the state of chessboard at position specified public SetChessBoard(ChessBoard, int); //This gets the state of chessboard at position specified public ChessBoard GetChessBoard(int); //This function tries to place both the pawns and returns the status of this attempt public bool PlacePawns(Pawn);

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  • Performance triage

    - by Dave
    Folks often ask me how to approach a suspected performance issue. My personal strategy is informed by the fact that I work on concurrency issues. (When you have a hammer everything looks like a nail, but I'll try to keep this general). A good starting point is to ask yourself if the observed performance matches your expectations. Expectations might be derived from known system performance limits, prototypes, and other software or environments that are comparable to your particular system-under-test. Some simple comparisons and microbenchmarks can be useful at this stage. It's also useful to write some very simple programs to validate some of the reported or expected system limits. Can that disk controller really tolerate and sustain 500 reads per second? To reduce the number of confounding factors it's better to try to answer that question with a very simple targeted program. And finally, nothing beats having familiarity with the technologies that underlying your particular layer. On the topic of confounding factors, as our technology stacks become deeper and less transparent, we often find our own technology working against us in some unexpected way to choke performance rather than simply running into some fundamental system limit. A good example is the warm-up time needed by just-in-time compilers in Java Virtual Machines. I won't delve too far into that particular hole except to say that it's rare to find good benchmarks and methodology for java code. Another example is power management on x86. Power management is great, but it can take a while for the CPUs to throttle up from low(er) frequencies to full throttle. And while I love "turbo" mode, it makes benchmarking applications with multiple threads a chore as you have to remember to turn it off and then back on otherwise short single-threaded runs may look abnormally fast compared to runs with higher thread counts. In general for performance characterization I disable turbo mode and fix the power governor at "performance" state. Another source of complexity is the scheduler, which I've discussed in prior blog entries. Lets say I have a running application and I want to better understand its behavior and performance. We'll presume it's warmed up, is under load, and is an execution mode representative of what we think the norm would be. It should be in steady-state, if a steady-state mode even exists. On Solaris the very first thing I'll do is take a set of "pstack" samples. Pstack briefly stops the process and walks each of the stacks, reporting symbolic information (if available) for each frame. For Java, pstack has been augmented to understand java frames, and even report inlining. A few pstack samples can provide powerful insight into what's actually going on inside the program. You'll be able to see calling patterns, which threads are blocked on what system calls or synchronization constructs, memory allocation, etc. If your code is CPU-bound then you'll get a good sense where the cycles are being spent. (I should caution that normal C/C++ inlining can diffuse an otherwise "hot" method into other methods. This is a rare instance where pstack sampling might not immediately point to the key problem). At this point you'll need to reconcile what you're seeing with pstack and your mental model of what you think the program should be doing. They're often rather different. And generally if there's a key performance issue, you'll spot it with a moderate number of samples. I'll also use OS-level observability tools to lock for the existence of bottlenecks where threads contend for locks; other situations where threads are blocked; and the distribution of threads over the system. On Solaris some good tools are mpstat and too a lesser degree, vmstat. Try running "mpstat -a 5" in one window while the application program runs concurrently. One key measure is the voluntary context switch rate "vctx" or "csw" which reflects threads descheduling themselves. It's also good to look at the user; system; and idle CPU percentages. This can give a broad but useful understanding if your threads are mostly parked or mostly running. For instance if your program makes heavy use of malloc/free, then it might be the case you're contending on the central malloc lock in the default allocator. In that case you'd see malloc calling lock in the stack traces, observe a high csw/vctx rate as threads block for the malloc lock, and your "usr" time would be less than expected. Solaris dtrace is a wonderful and invaluable performance tool as well, but in a sense you have to frame and articulate a meaningful and specific question to get a useful answer, so I tend not to use it for first-order screening of problems. It's also most effective for OS and software-level performance issues as opposed to HW-level issues. For that reason I recommend mpstat & pstack as my the 1st step in performance triage. If some other OS-level issue is evident then it's good to switch to dtrace to drill more deeply into the problem. Only after I've ruled out OS-level issues do I switch to using hardware performance counters to look for architectural impediments.

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  • Red Gate Software announces speaker line up for US SQL in the City tour

    SQL in the City is a free, full day training and networking event for database professionals. After the success of last year’s event, Red Gate has expanded the event to cover six cities from sea to shining sea, including: New York, Austin, San Francisco, Chicago, Boston, and Seattle. Compress live data by 73% Red Gate's SQL Storage Compress reduces the size of live SQL Server databases, saving you disk space and storage costs. Learn more.

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